# Why can’t ice cubes from a freezer freeze water?

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If a glass of water is mostly ice with some water, how come the water doesn’t freeze? Is it something to do with the conduction heat transfer between the air and the glass of water? Im assuming that the water would freeze in a vacuum.

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Water boils in a vacuum.

Ice cubes don’t freeze water because the water is getting colder by the ice cubes warming up. Heat is transferred between them until an even temperature is reached. The ice would have to be exceptionally cold, and stay cold for a long time, to freeze water.

Heat is an energy.

A system either has heat or it does not have heat.

We call a system that does not have heat “cold.” Especially when the surrounding temperature is higher and the object’s temperature is relatively lower.

When you pour water into the cracks.between ice, the water has more heat energy than the ice itself. This melts the surface of the ice.

As the ice steals heat from the water, it freezes the water on its surface.

Because the surface of the ice is both melting from gaining heat and freezing from having its heat stolen, a barrier of equilibrium is more or less formed on the surface of the ice where you have this layer that is constantly trying to melt and freeze at the same time.

So you have a layer thats hotter than the ice on the outside, melting. A transition layer where the temperature is likely ranging through freezing from not freezing, we’ll say 0 to 1C, and then a layer closest to the core of the cube where the ice is solid and anything from that point on is solid.

Since the surrounding air is then warmer than the water and your hand contacting the glass is warmer, heat energy moves from those heat sources and into the cup, then from the cup to the water to continue melting the surface that the core is trying to freeze.

heat flows from hot to cold, so the water is heating up the ice. It takes a lot more energy transfer to convert from water to ice. Normally the freezer is providing that continuous cooling energy.

In a vacuum the water would boil away.

Freezing water releases quite a bit of heat (or, if you prefer, “takes quite a bit of cold”). In fact, the amount of energy required to melt ice is almost the same as the amount required to raise it from freezing to boiling once it has melted.

The ice just isn’t cold enough. A very cold freezer has ice at maybe -10 C, meaning you’d need an ice-to-water ratio of 10:1 or so for the warming of the ice to cool the water down enough to freeze.

In order for the liquid water to freeze it would need to lose heat. In a glass of ice water the heat will be absorbed by the ice. The ice absorbing heat from the liquid water cools the liquid water, but the ice will absorb enough heat to melt long before the liquid water has given up enough heat to freeze.

It is is possible for liquid water to spontaneously form into solid ice given the appropriate pressure and temperature, but a glass of ice water in a normal room likely doesn’t meet those criteria.

The ice and water want to reach the same temperature (thermal equilibrium). Usually your glass of ice-water is sitting in a room full of air at room temperature, so the ice and water both want to get to room temperature, which is above the freezing point, meaning the ice melts.

If you put the glass of ice-water in the freezer, the water will freeze because the ambient temperature is now below the freezing point.

If you put the glass in a vacuum, the water will simultaneously freeze and boil until all the liquid is gone. Then the ice will sublimate until all that’s left is water vapour.

To summarize, a room full of air has so much heat, it can transfer that to the glass and water and ice until they all reach room temperature while imperceptibly lowering the temperature of the air. You would need a much smaller space for the capacity of the ice to store heat to freeze the water in room temperature air.

consider a 20ml iceblock at -2.c going into a 200ml glass of water at 26.c

thats 20 x -2 encountering 200 x 26

this is not math matching the real values just example math.

the -40 ice enters the +5200 water averaging out at 5160. so you end up with 220ml at ~23.5.c

to get the glass to freeze that block of ice would need to counter the total 5200 so that 20ml ice would need to be -5200 to bring it down to 0 or -260.c not including air or the glass itself.